题目

India now leads the world in smartphone growth. It saw a 55% increase in the number of smartphones in 2014. The number of Web users increased by 37 %. Smartphones were the source of 65 % of its Internet traffic and 41 % of its e-commerce, according to a report by the analyst Mary Meeker, titled “Internet Trends 2015”. India’s Internet boom has started. Within three or four years, almost every adult in India will own a smartphone. They will be used to order goods, read news, monitor crop growth and so on. Indian adults will be very interested in these devices just as young Americans 如图，在矩形ABCD中，DE⊥AC于点E，设∠ADE＝α，且cosα＝0.6，AB＝4，则AC的长为 [　　] A． B． C． 3 D．